Mum passed away 2 days ago.

I’m so broken hearted. Mum fell asleep for the last time on Friday after living with Vascular dementia, respiratory failure and heart failure for so long. She was diagnosed with a lung mass Wednesday and passed away 2 days later. I feel like I have lost mum so many times over the last 2 years with her dementia but wasn’t prepared for her passing away. I don’t know how to cope emotionally. I have the support of my 3 siblings and my husband and children, so why do I feel so alone? 
We need to start making funeral arrangements tomorrow, this is all so hard.